The objectives of this project are to study the morphological effects of tooth pulp extirpation, extraction of teeth and exfoliation of deciduous teeth on the trigeminal system. Light and electron microscopical methods will be used to analyze and evaluate the sequence of acute and chronic alterations in the sensory neurons of the trigeminal ganglia, their central axons and synaptic endings in the main sensory and spinal trigeminal nuclei. Extirpation of tooth pulps and extraction of teeth will be performed on adult cats and a variety of short-term and long-term postoperative survival times will be studied. Young cats undergoing various stages of tooth replacement will be used to determine possible changes caused by exfoliation of deciduous teeth and eruption of permanent teeth upon neuronal structures of the trigeminal system. Retrograde nerve cell changes in the trigeminal ganglia will be correlated with the study of degeneration of their axons and synapses in the brain stem trigeminal nuclei. The type of cells and axons, the population and character of synapses and their distribution in the brain stem, the precise sequence and pattern of degeneration, the possible transneuronal effects and potential regenerative capabilities of these axons and synapses will be studied and characterized in each of the preparations. The project will be useful in providing new information about the anatomical representation for the teeth within the central nervous system and will also provide possible morphological explanations for certain sensory alterations, including pain-related symptoms, associated with dental surgery, endodontic therapy, tooth loss or trauma involving these structures.